Electronic engine controllers typically utilize an Exhaust Gas Oxygen sensor (EGO) to provide an indication of the actual air/fuel (A/F) mixture combusted by the engine. EGO sensors take a variety of forms, but most production vehicles utilize a switching type EGO sensor which provides a first voltage level to indicate that the concentration of oxygen in the exhaust gas is rich of stoichiometry, and a second voltage level to indicate that the concentration of oxygen in the exhaust gas is lean of stoichiometry.
As engine components age, the changing characteristics of the components causes the dynamic response of the engine to change. For instance, deposits which form on the intake valves cause subtle changes in the fuel flow. Switching type EGO sensors which provide only a qualitative indication of the A/F ratio combusted by the engine, cannot, by themselves, provide an indication of the subtle changes brought about by aging of engine components.
It is accordingly an object of the present invention to provide an engine controller which can determine from information generated by a switching type EGO sensor the dynamic response of an engine and compensate for the subtle changes in the dynamic response which may have been due to long term effects such as aging.